The present invention relates to an air motor to be used as a driving power source of industrial machines and equipment such as an air grinder for grinding and polishing operation or handpieces for odontotherapy.
An air motor to be used as a driving power source not only for grinding and polishing operation but for handpieces and so forth for odontotherapy is generally of the construction as shown in FIG. 12.
Briefly, the air pack comprises a grinding-polishing tool unit which rotatably supports a desired grinding-polishing tool 100 and is enclosed in a casing 500; a power unit 900 including a front retainer 11a, a rear retainer 11b, a rotor 111 rotatably supported by the front and rear retainers 11a and 11b and having a plurality of vanes 121 which can be moved in and out, a stator 101 holding the rotor 111 located between the front retainer 11a and the rear retainer 11b, and an air supply passage 600 and an air discharge passage 700, which are all enclosed in a casing 800; and an air supply joint 3 for adjusting the amount of compressed air to be supplied to the power unit 900. The grinding-polishing tool unit 400 is threadedly connected to the power unit 900, and the air supply joint 3 is formed of a valve body 901 having an air supply hole 902 through which the air is supplied to the power unit 900, and a grip portion 5 movably engaged by a screw with the valve body 90 for adjusting the amount of opening of the air supply hole 902.
In the case of the above-described prior art, the forward end of the valve body 901 is threadedly engaged with the inner peripheral surface of the casing 900 of the power unit 900 into contact with the retainer 11b, and further the engaged portion a is fixedly secured with adhesive; therefore when disengagement of this engaged portion a is required, the adhesive b must be removed after softening the adhesive b by heating up to around 100.degree. C. The above-described operation, however, is very inconvenient because it requires a special technique for replacement of the power unit 900 without deteriorating durability thereof.
Furthermore, the internal pressure of the power unit 900 (the internal pressure of the stator 101) becomes very high during operation and leaks out, though little despite of an airtight design, to thereby force a lubricant such as grease out from a bearing section 131 of a rotor shaft 111a, resulting in oil starvation and accordingly seriously deteriorated durability due to a failure in withstanding high-speed operation. In addition, because of the construction that vibration of the power unit 900 passes directly to a user's hand and fingers, the user will be likely to feel fatigued.
Furthermore, the grip section 5 opens the valve when turned counterclockwise and closes the valve when turned clockwise. However, if the counterclockwise turn of the grip section 5 is carelessly kept on, the grip section 5 will in some case drop from the air supply joint 3. Therefore the air motor is not necessarily convenient for the use lacking in a special knowledge concerned.